THE STRENGTH OF MULTILAYERED COMPOSITES UNDER A PLANE-STRESS STATE

The paper presents a model that describes the deformation and failure processes of multilayered hybrid composites in a state of plane stress . The model, which can be considered as a structural-phenomenological one, is a coupled deformation/failure model (DFM). According to the mo del, except for two common states of the composite laminate-the initia l state (monolithic material) and the final state (completely broken m aterial)-there exists a group of intermediate states, namely the mater ial with cracks. Within the group, we can distinguish two further sub- groups of material states: (I) with open cracks and (2) with closed cr acks. The total number of states equals eight (four in the 'open-crack ' group). The algorithm of successive stress loading is a natural one for the model. The low shear modulus of modern polymeric composites of ten results in significant changes in the initial reinforcing angles o f the plies as a consequence of shear strains, which is why the model considers the effects of the 'structural non-linearity' of the laminat e. The algorithm is capable of predicting both stress/strain curves an d failure envelopes for multilayered composites under a variety of loa ding conditions. Theoretical predictions are presented for a number of cases provided by the organisers of the failure exercise. (C) 1998 El sevier Science Ltd. All rights reserved.